I agree with the coments on FO3 that it has atmospheric post apocalyptic setting, I for one have watched the movie ''The Road'' and playing the game I was emerged in to the world.Where without a doubt FO:NV is better crpg in so many aspects, I didn't felt like I was in the wasteland.So yes for the setting to play once or twice for the doubt can be FO3.
But for a crpg fan the FO:NV is obligatory.